Table 6.

Intervention studies on eggs and metabolic risk markers.

Author, Year	Study Design	Intervention	Number of Participants	Outcomes	Results
Andersen, 2013 [69]	SBRCT, parallel	3 eggs/day or yolk-free egg substitute + moderately carbohydrate-restricted diet for 12-weeks	37 adults with MetS (30–70 y)	Blood lipids	Egg group had significantly greater increase in HDL-c vs. egg substitute group No significant change to LDL-c or TC.
Blesso, 2013 [70]	SBRCT, parallel	3 eggs/day or yolk-free substitute + moderately carbohydrate-restricted diet for 12-weeks	37 adults with MetS (51.9 ± 7.7 y)	Carotenoid status	Egg group had significantly increased plasma lutein and zeaxanthin vs. egg-substitute group. Significant lipoprotein enrichment with lutein and zeaxanthin in egg group only.
Blesso, 2013 [71]	SBRCT, parallel	3 eggs/day or yolk-free substitute + moderately carbohydrate-restricted diet for 12-weeks	37 adults with MetS (51.9 ± 7.7 y)	Blood lipids, insulin resistance	Egg group had significantly greater increases in HDL-c, large HDL-c particles, LCAT activity and HDL-c and LDL-c diameters vs. egg-substitute group Egg group had significantly reduced plasma insulin, HOMA-IR and VLDL-c vs. egg-substitute group.
Thomas, 2022 [73]	RCT, crossover	2 eggs/day with 70 g spinach or yolk-free egg substitute with 70 g spinach + meat-free diet for 4 weeks	24 adults with MetS (49.3 ± 8 y)	Oxidative stress, inflammation	Egg group had significantly lower plasma malondialdehyde compared with egg substitute group. No significant differences in other biomarkers. MetS characteristics reversed in 11 participants during the egg diet and 7 participants during the egg substitute diet.
Thomas, 2022 [72]	RCT, crossover	2 eggs/day with 70 g spinach or yolk-free egg substitute with 70 g spinach + meat-free diet for 4 weeks	24 adults with MetS (49.3 ± 8 y)	Inflammatory markers, blood lipids	Egg group had significant reduction in weight and BMI compared with egg substitute diet. Egg group had significant increase in HDL-c, large HDL-c particles and choline compared with baseline Plasma zeaxanthin rose significantly during egg diet compared with egg substitute diet and with baseline.
Thomas, 2022 [74]	RCT, crossover	3 eggs/day or choline supplement for 4 weeks	23 adults with MetS (35–70 y)	Plasma TMAO, carotenoid status, gut microbiome	Significant increases in plasma choline seen in both interventions No change to plasma TMAO or gut microbiome during either intervention. Plasma lutein and zeaxanthin increased during egg intervention relative to baseline and choline treatment.

Key: BMI, body mass index; HDL-c, high-density lipoprotein cholesterol; HOMA-IR, Homeostatic Model Assessment for Insulin Resistance; LCAT, Lecithin-cholesterol acyltransferase enzyme; LDL-c, low-density lipoprotein cholesterol; MetS, metabolic syndrome; RCT, randomised controlled trial; SBRCT, single blind randomised controlled trial; TC, total cholesterol; TMAO, trimethylamine N-oxide; VLDL-c, very-low-density lipoprotein cholesterol; y, years.